The present invention relates to a novel assembly for fastening together or supporting various elongate articles such as pipes, cables, rods, tubing or hoses. The invention is particularly useful for securing electrical, fuel, oil, hydraulic or pneumatic lines in harsh environments subject to sustained vibration, such as found along the engine mounting frame of aircraft or in other aeronautical, astronautical, industrial or automotive environments.
In the inventor's experience as an aircraft mechanic and authorized inspector, many of the planes arriving for service required additional work due to problems in their original fastening systems. Three fastening methods that have performed more adequately than others under the above-mentioned conditions are rubberized cushioned clamps, lacing cord and cable ties.
Rubberized cushioned clamps are metal straps which have screw holes at each end and a rubber liner. A separate clamp is bent around each of the hoses or cables to be connected and the clamps are then fastened together, through the holes at their ends, by a screw and nut. To fit the many sizes of hoses or cables in use, many different sizes of straps must be kept in stock and a moderate expenditure of time is involved in properly bending the straps and in screwing the nut fully into position. Furthermore, lubricating solvents, such as engine oils, can attack the thin rubber liner separating the hose or cable from the metal strap, so that the edges of the metal strap will gradually cut through the hose or cable and cause line failure.
Lacing cord is a stretchy plastic cord that comes in 100 or 1000-ft spools. The cord is cut to length, lashed around the hoses or cables to be connected, and thereafter tied. Proper lashing and tying of the cord requires at least 6 to 8 inches of clearance around the fastening area and is virtually a lost art because such labor-intensive activity is uneconomical at today's labor rates. High temperatures can loosen the plastic cord and cause line failure if, for example a segment of the fastened hose or cable bunches together and establishes contact with a nearby moving part or hot surface.
Cable ties are generally nylon straps that have a free end adapted for insertion through a self-locking head at their second end. They can be used in combination with spacers of a type such as disclosed in Moody et al. U.S. Pat. No. 3,668,744, McSherry et al. U.S. Pat. No. 4,562,982 and Gooding U.S. Pat. No. 4,819,897. During use, for example, with a spacer of the type disclosed in McSherry et al., the cable tie is passed through an opening in the annular member which comprises the spacer, around one of the cables, back through another opening in the spacer and around the other one of the cables, the tie thereupon being closed and tightened so that each cable is secured in lengthwise, mutually parallel relation across opposite marginal edges of the annular member. With this arrangement, if the strap is initially overtightened, or if external forces cause the cables to vibrate laterally relative to one another, the nylon strap being of nondeformable material can pinch into or chafe the cables. Additionally, the compressive forces which are exerted by the vibrating cables on the narrow edges of the spacer can cause the spacer to crack and split open. One approach for mitigating these difficulties is suggested by the separator clip of Moody et al., where each cable is held to a separate arm of the clip by a separate cable tie and where the arms are able to flex toward and away from each other since they are held together, only at one end, by a resilient stem.
Another problem encountered is external forces which cause cables or hoses to vibrate longitudinally relative to one another. Where the spacer used relies on a notched channel to receive each cable or hose, as shown in McSherry et al., only that limited outer portion of each cable or hose which is arranged adjacent either side of the notch will establish contact with the channel. Because only a limited area is then provided for frictional engagement, slippage or creep may occur between the cables or hoses, and the cables or hoses may stretch and burst or may bunch up and make contact with hot surfaces or moving parts. Other prior art spacers, such as shown by Gooding, form the channel so as to match the curvature of the cables or hoses to be held. This approach, however, requires that a variety of spacers be made and retained in stock to match the different sizes of cables or hoses encountered.
Another problem with the notched channel found on spacers of the type shown in McSherry et al. is the tendency for solvents, such as oils and other lubricants, which promote cable slippage and corrosion, to become trapped inside the space formed between the rounded outer portion of the cable and the apex of the channel.
The present invention is directed toward a fastening assembly of novel design and construction which is suitable for fastening together all manner of elongate articles and which overcomes the aforementioned drawbacks of prior art devices used in the applications described.